The present invention concerns a device for cleaning surfaces, particularly large surfaces that have at least partly limited availability for conventional methods of cleaning, including ship hulls and the like.
It is a considerable challenge to develop equipment for large surfaces such as ship hulls, partly due to their limited availability being partly submerged in water. On the other hand, due to fouling of the surfaces with marine organisms that make the surfaces rough and not smooth, a rather frequent cleaning is required. A ship hull covered with layers of such organisms will have a significant increase in fuel consumption as a result of the increased friction between the hull and the water. In this connection it should be noted that an increase in friction of 1% leads to an increase in fuel consumption of 3%.
Furthermore ship hulls are commonly coated with toxic ship-bottom paints containing organic tin compounds that it is highly desired remain in place during the cleaning operation, as it else will lead to poisoning of marine organisms. It is thus a challenge to develop equipment that removes impurities from the surfaces but that does not or to only a limited extent damage any layers of ship-bottom paints present.
Norwegian patent No. 310 902 (Andorsen) describes a cleaning apparatus for marine constructions, primary closing nets and fish farming net cages. The apparatus comprises a rotary disc provided with nozzles along the disc periphery. The disc is suspended in a line arranged to be moved mainly vertically along a vertical surface to be cleaned. By directing the nozzles with a certain inclination a so-called “foil” effect is obtained, which is understood to mean a kind of attraction between the disc and the surface to be cleaned.
Norwegian patent No. 313 746 (Andorsen) describes a cleaning apparatus for marine constructions, mainly ship hulls, offshore construction, fish farming plants, and the like. The apparatus comprises nozzles arranged on rotor members and a cleaning unit typically comprises three or five such rotor members. The main unit is suspending by a wire, chain or the like. According to the patent it is important to reduce the size of the rotor members that typically have a diameter less than 25 cm, to thereby increase their speed, which is assumed to lead to an improved cleaning effect at a given water pressure. From this it seems to be clear that the water pressure provides the driving force for the rotor members. An operational pressure of 200 to 250 bars is mentioned.
U.S. Pat. No. 3,946,692 concerns a device for cleaning of surfaces under water provided with wheels, having cleaning members comprised by circularly, rotary brushes arranged in a manner to be create an attraction force between the brushes and the surface. The device typically has three brushes and the attraction force per brush is said to be about 220 kg, i.e. abut 660 kg for the entire device/vehicle. The brushes are powered by separate hydraulic motors and the rotary speed is typically between 700 and 1200 rpm. The brush diameter is typically 400 mm. There is no mention of supply of pressurized water in this patent.
U.S. Pat. No. 4,574,722, like U.S. Pat. No. 3,946,692, concerns a “vehicle” provided with brushes to clean surfaces such as ship hulls under water. A drawing shows that a little surface vehicle is intended to act as a “buoy” for the vehicle when the latter is moved along a vertical surface of a ship. An important feature of this device is the fact that each brush has a flexible suspension mechanism that shall ensure good cleaning even when the surface to be cleaned is not flat. The vehicle also comprises a buoyancy tank.
U.S. Pat. No. 4,926,775 also concerns a cleaning device intended for use on mainly vertical surfaces under water. The apparatus comprises a set of nozzles (or at least one nozzle) arranged to spray water under high pressure against a surface, the nozzles being arranged on (at least) one rotary disc, the rotational axis of which is mainly perpendicular to the surface to be cleaned. It is particularly pointed out that the nozzles are obliquely arranged to provide the spraying water with a tangential motion component, leading to a reactive force that sets the disc in rotation. In addition one or more of the nozzles are directed away from the surface to be cleaned in order to maintain the apparatus in a position close to the same surface.
U.S. Pat. No. 5,884,642 concerns a movable vehicle for cleaning of metallic surfaces such as ship hulls by application of pressurized water. The movement is conducted by means of cog wheels and chains comprising magnetic elements or sections. The patent is largely occupied with the individual control of the wheels to provide the vehicle with a convenient movability/maneuverability. Cleaning nozzles are distributed along a rotation symmetrical central arm under the vehicle, said arm being arranged to pivot around a central axis (48) through which the water is supplied, such that the nozzles draw circles with different radii. Nothing in this patent indicates that the arm may rotate against the direction of obliquely arranged nozzles, and it is therefore assumed that the mechanism for rotation is the same as described in U.S. Pat. No. 4,926,775.
U.S. Pat. No. 6,425,340 concerns a device for cleaning surfaces under water, utilizing a permanent magnet to attach the device to e.g. a ship hull or the like. The cleaning device comprises an “ultra-high pressure water jet system” and is intended to remove also “coatings” like paint etc. A water pressure of 25 000 psi or 1725 bar is indicated and the system comprises at least one pivotal nozzle. Furthermore the device includes a surrounding sheath that covers the area around the nozzle orifices tightly against the hull in order to collect material that comes loose, so that it does not get lost to the environment. It is worth noticing that the nozzle or nozzles according to this publication are rotating around themselves, they are not mounted on a rotating disc. This feature is evident e.g. by FIG. 5 (rotary part 32) and by column 9, lines 15-16 and lines 30-33 of the description. This publication by the way provides a broad reference to prior art publications in the area.
U.S. Pat. No. 5,048,445 concerns a device for the same purpose as the publications discussed above, and describes “Thruster assemblies” for propulsion of the device/vessel. The nozzles are arranged on one or more manifold(s) that in certain embodiments may have the shape of a rotatable ring. It is mentioned, cf. col. 9, lines 23-35, that the nozzles for this purpose are obliquely arranged, so that the counter force from the water leaving the nozzles under a high pressure, sets the ring shaped manifold supporting the nozzles in rotation with a rotational speed of typically 90 rpm.
There are also a number of cleaner devices for land based purposes with a rotary head for water flushing or spraying, like the one described in U.S. Pat. No. 3,829,019. This patent describes an apparatus for cleaning of floors and walls and comprises a housing that covers rotating arms furnished with water channels and nozzles for discharging water under pressure against a surface in the form of wall, a floor (terrace) or the like. The rotation of the arms is provided by means of obliquely arranged nozzles on the arms but some of the nozzles may also be directed obliquely in the opposite direction of the rotation powering nozzles. While the nozzles determining the direction of rotation have an angle typically 30° “backwards”, the oppositely oblique nozzles have an inclination typically 15° forward. With the presumption that the backward pointing nozzles are not fewer than the forward pointing nozzles, the sum of the force components of the former in the direction of rotation will be larger than the sum of force components of the latter, since the former has a direction closer to the direction of rotation. The force components of the forward pointing nozzles do, however, reduce the rotation to a speed less than what would have been obtained if such nozzles were not present. The apparatus according to this US patent is not suited for cleaning surfaces under water, since the rotating arms provided with nozzles are localized in a substantially open construction and would be surrounded by water that would drastically reduce the arms ability to rotate if the apparatus is submerged in water.
U.S. Pat. No. 4,314,521 teaches an apparatus and a method for cleaning surfaces under water. The apparatus comprises both brush and nozzles attached to a member arranged to rotate and it is mentioned that the rotation may either be effected by means of obliquely arranged nozzles or by means of e.g. hydraulic motors. The apparatus is mainly intended to be controlled by divers and nothing specifically is said about the arrangement of the nozzles apart from the obvious that they must be oblique in the cases where they are to effect the rotation. Liquid is provided from a pump under the surface and in addition the apparatus needs supply of air from the surface to rotate sufficiently easy. The rotating member is hidden beneath a housing that covers all sides of the brush and the member furnish with nozzles, except the side facing the surface to be cleaned.
In short a number of devices for cleaning surfaces like ship hulls and the like comprising both use of brushes and spraying with pressurized water through nozzles. Among the devices based on nozzles some have nozzles arranged on members arranged for rotation, some with nozzles on an arm, some with nozzles on a ring shaped member and some with nozzles arranged on a “whole” disc.
It is a significant challenge to provide a sufficient cleaning of fouled surfaces of a ship hull without damaging or removing parts of the ship-bottom paints applied to the hull. At the same time it is a considerable challenge when transferring liquid under high pressure to a high-speed rotation disc or the like, to establish a liquid coupling that is reliable and leakage free over a longer period of time.